A user role defines permissions for users to perform a group of tasks. In a default WordPress installation there are some predefined roles with a predefined set of permissions. These roles are Super Admin, Administrator, Editor, Author, Contributor, and Subscriber. Each roles has a certain number of set tasks it is allowed to perform that are known as “capabilities”. There are numerous capabilities including “moderate_comments”, “publish_posts”, and “edit_users”. Although every role has a predefined set of capabilities, new capabilities can be added and removed from each role. User roles are very handy when it comes to multi-author WordPress sites.
As far as the default roles are concerned the Super Admin has the highest level of access while the subscriber has the least. The subscriber role only allows the user to read posts but not write anything. The Contributor can write posts but not publish them. The author role can write and publish their own posts while Editors can do the same for their own posts as well as others. The administrator has access to all administration features within a single site and the Super Admin has access to the entire network if it exists.